Cylinder Area

K

ken-r-mer

Senior Member
Trying to do some calcs. Is there any numbers known as to the sq inch area of the head area? I can find the cubic centimeter volume from the many head mfrs but not the surface area. Reason is I'm trying to figure out how the different head gasket thicknesses affect the compression ratio.
 
if i understand the question (and i'm not certain i do)...

because the purpose involves the surface area of a head gasket and not its volume nor the actual area of the head itself, may it be reasonable to ask the question like this: "what is the area of the head gasket minus the area of the holes in the head gasket"?

if so...to get a reasonable approximation, i would multiply the length of the head gasket by its width and then subtract from that the sum of the areas of the holes in the gasket. i.e. the holes for the cylinders, the holes for the studs, and the holes for the coolant passages. fortunately they are most often circles.

and the formula for calculating the area of a circle is: 4/3 times PI times the radius of the circle squared. you can thank Archimedes for that one!

...get out your calculator! :)
 
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If you decide not to try and calculate it you could draw the gasket shape onto a piece of graph paper and count the squares. If less than half a square don't count it, if more than half, count it. Old fashioned but will give a decent estimate.

Mart.
 
Making sure my blower setup of 6-7 psi boost will allow me to know the needed minimum octane rating to avoid pre-detonation. If I knew the surface area of bore/valve area, I would be able to determine the added volume to the head cc with the varying head gasket thicknesses, allowing for compression calculation in a table found in Joe Abbin's Performance handbook. The compressed std thickness of typical head gaskets is 0.055". Cometic makes variable thickness head gaskets for the flathead (from .027" all the way up to 0.140"). Figure it's safer to play with varying head gasket thicknesses vs grinding on a set of $1500 heads to tweak the compression ratio. Will also be doing clay testing to make sure I'm close to the "quench' thickness of 0.40" over the piston area and valve clearance since I'm getting a Schneider P-3/8 cam that has 0.375" lift. The variables I've see are boost (pulley size), head cc's (a low compression head in combination with head gasket thicknesses), and octane ratings. Surprisingly the Edelbrock 1116 74cc heads at less than $900 have better intake/exhaust air flow numbers in Abbin's head comparison chart, as well as a lower compression ratio compared to $1500 Offy 425 64cc's. Unfortunately no numbers are available for the $1750 Navarro's 75cc blower heads. H&H was no help regarding air flow numbers on the Navarro's.I'm still fighting the Offenhauser and Navarro name mystique. Weiand heads had top 3 head flow numbers but at 64cc has a high compression ratio and are no longer being made.
 

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Mart said:
If you decide not to try and calculate it you could draw the gasket shape onto a piece of graph paper and count the squares. If less than half a square don't count it, if more than half, count it. Old fashioned but will give a decent estimate.

Mart.
Click to expand...

An alternative would be place a head gasket on a flat piece of metal or better, glass. Hold the gasket down with some weights. Fill the gasket cutout for the piston and valves with Very fine sand or such. Carefully drag a sharp edged straight rule across the top of the gasket.

Remove the gasket from the glass or metal and measure the sand volume in a graduated cylinder.

Since the volume is equal to the area times the height, you can figure the gasket thickness as so:

V = Area X Thickness
V = A X T, noting that the A doesn't change only the volume based on the gasket height or thickness.

For the required V or Vr, calculate the Tr as so,

V/Vr = T/Tr
 
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